Handheld or mobile computers are widely used, such as in different field mobility environments. For example, these computing devices may be used by mobile field service and transportation workers to allow different types of mobile operations, such as in-field computing, radio frequency identifier (RFID) scanning, barcode scanning, and communication with remote external devices, among others.
For RFID scanning, RFID scanners may use one or more RFID methods for different applications, including for smart cards, supporting maintenance tasks, identification badges, tracking objects in manufacturing, retail inventory management, etc. An RFID tag can be attached, e.g., to an inventory object. An RFID apparatus can be configured with an RFID reading device including one or more antennas to read the memory of an RFID tag attached to an inventory object.
The RFID apparatus may be a handheld device with integrated RFID reading capabilities that can read RFID tags from a range of distances, such as during a retail floor inventory operation. It is desirable to have reliable communication links between the RFID apparatus and the RFID tags, which may include numerous RFID tags responding at the same time. In RFID systems, both forward (reader-to-tag) and reverse (tag-to-reader) links are important. In operation, the overall system performance can be limited either by the tag sensitivity (“tag-limited” or “forward-limited”) or by the reader sensitivity (“reader-limited” or “reverse-limited”).
In practical scenarios, it is desirable to have the RFID systems (reader and tag) operating robustly with enough RF margins on both forward and reverse links, so that the tag does not drop out suddenly if the environment or the distance to the tag changes. In addition, sometimes during a singulation stage (setup process), multiple tags backscatter at the same time and signals from several tags collide at the reader. In most cases, the multiple signals cannot be simultaneously resolved by the reader because the backscatter modulating impedances of the tags are fixed and cannot be changed, thus slowing down the tag singulation and identification process.
Thus, because of the limitations of conventional devices and methods, communication between the reader and multiple tags may be interrupted or not operate satisfactorily, thus resulting in extra time and expense in the RFID communication process.